#region Copyright & License

//
// Copyright 2001-2005 The Apache Software Foundation
//
// Licensed under the Apache License',' Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing',' software
// distributed under the License is distributed on an "AS IS" BASIS','
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND',' either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#endregion

using System;
using System.Net;

namespace log4net.Util.TypeConverters {
  /// <summary>
  /// Supports conversion from string to <see cref="IPAddress"/> type.
  /// </summary>
  /// <remarks>
  /// <para>
  /// Supports conversion from string to <see cref="IPAddress"/> type.
  /// </para>
  /// </remarks>
  /// <seealso cref="ConverterRegistry"/>
  /// <seealso cref="IConvertFrom"/>
  /// <author>Nicko Cadell</author>
  class IPAddressConverter : IConvertFrom {
    #region Implementation of IConvertFrom

    /// <summary>
    /// Can the source type be converted to the type supported by this object
    /// </summary>
    /// <param name="sourceType">the type to convert</param>
    /// <returns>true if the conversion is possible</returns>
    /// <remarks>
    /// <para>
    /// Returns <c>true</c> if the <paramref name="sourceType"/> is
    /// the <see cref="string"/> type.
    /// </para>
    /// </remarks>
    public bool CanConvertFrom(Type sourceType) {
      return (sourceType == typeof (string));
    }

    /// <summary>
    /// Overrides the ConvertFrom method of IConvertFrom.
    /// </summary>
    /// <param name="source">the object to convert to an IPAddress</param>
    /// <returns>the IPAddress</returns>
    /// <remarks>
    /// <para>
    /// Uses the <see cref="IPAddress.Parse"/> method to convert the
    /// <see cref="String"/> argument to an <see cref="IPAddress"/>.
    /// If that fails then the string is resolved as a DNS hostname.
    /// </para>
    /// </remarks>
    /// <exception cref="ConversionNotSupportedException">
    /// The <paramref name="source"/> object cannot be converted to the
    /// target type. To check for this condition use the <see cref="CanConvertFrom"/>
    /// method.
    /// </exception>
    public object ConvertFrom(object source) {
      var str = source as string;
      if (str != null && str.Length > 0)
        try {
#if NET_2_0
  // Try to resolve via DNS. This is a blocking call. 
  // GetHostEntry works with either an IPAddress string or a host name
					IPHostEntry host = Dns.GetHostEntry(str);
					if (host != null && 
						host.AddressList != null && 
						host.AddressList.Length > 0 &&
						host.AddressList[0] != null)
					{
						return host.AddressList[0];
					}
#else
          // Before .NET 2 we need to try to parse the IPAddress from the string first

          // Check if the string only contains IP address valid chars
          if (str.Trim(validIpAddressChars).Length == 0)
            try {
              // try to parse the string as an IP address
              return IPAddress.Parse(str);
            } catch (FormatException) {
              // Ignore a FormatException, try to resolve via DNS
            }

          // Try to resolve via DNS. This is a blocking call.
          IPHostEntry host = Dns.GetHostByName(str);
          if (host != null &&
              host.AddressList != null &&
              host.AddressList.Length > 0 &&
              host.AddressList[0] != null)
            return host.AddressList[0];
#endif
        } catch (Exception ex) {
          throw ConversionNotSupportedException.Create(typeof (IPAddress), source, ex);
        }
      throw ConversionNotSupportedException.Create(typeof (IPAddress), source);
    }

    #endregion

    /// <summary>
    /// Valid characters in an IPv4 or IPv6 address string. (Does not support subnets)
    /// </summary>
    static readonly char[] validIpAddressChars = {
                                                   '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b',
                                                   'c', 'd', 'e', 'f', 'A', 'B', 'C', 'D', 'E', 'F', 'x', 'X',
                                                   '.', ':', '%'
                                                 };
  }
}